1. Field of the Invention
The present invention relates to resource scheduling in a computer.
2. Related Art
Enterprise level general-purpose operating systems, both workstation and server, are traditionally designed for efficient resource utilisation. Applications share a common set of resources, which are initially scheduled according to their priority and then in a fair weighted manner. This approach results is both an efficient and fair division of resources to user-level applications. However, certain applications, in particularly multimedia processing applications, are inherently sensitive to resource availability. As a result, the use of priority-based resource federation policies often results in such applications failing to meet their processing goals.
U.S. Pat. No. 5,812,844 discloses a method of CPU scheduling, using the Earliest Deadline First scheduling of threads. However, there is no notion of resource admission in this invention and therefore guarantees are only best-effort and the scheduling is only single level, based on threads. Scheduling dependent upon process priority and/or urgency is not included. EP-A-0 798 638 discloses a further approach to CPU scheduling, in which a number of processes exist as a group. In turn the group is ‘scheduled’ by increasing its priority, although the scheduler cannot guarantee that a process within a group will be scheduled.
Conventionally, relatively complex processing is required of the scheduling process at the stage where a process is granted access to a resource. The present invention enables a reduction in the complexity of the processing at the access grant stage by providing for reservation of resources in advance.